" I disagree with Lynn in as much as hot foam touching my back has to be hotter than mesh."

I don't think we disagree, as I stated that the Exos allows you to cool quicker. However, I am also comparing it to a pack such as the LuxuryLite where there is no fabric of any kind touching your back, and the difference is huge. The Exos is my pick of the bunch, and really comes into it's own on winter hikes where minimising sweat is a key goal for me, but it's not a patch on a true external frame pack in terms of ventilation.

I have a Dueter 42 Pro and a REI Venturi. I live and hike in a hot as you can get climate, but without the humidity of other places.

I use these packs only when carrying heavy loads of water in hot temperatures. And, the heavier the load, the hotter and sweatier you are going to get. The packs help in these situations, but the mesh panels makes packing gear less than comfortable.

If I do not need to carry a lot of water (i.e. 2 or more gallons), I wouldn't even consider using them. Lighter pack, usually means less sweating. And if your total pack weight is truly lightweight, it is easy to carry it slung over one shoulder for periods of time.

>Lighter pack, usually means less sweating. And if your total pack weight is truly lightweight, it is easy to carry it slung over one shoulder for periods of time.

I don't know how much sense that makes Nick. A pack that is 1 lb lighter but sits on your back seems like it will still make you sweat more than one that holds that extra lb away from you. (If there is even 1 lb difference in what you are talking about.)

You live right by the awesome Skyline Trail. I have sweated many times on it and don't remember many times I could/wanted to carry my pack on one shoulder. I did want to throw it away a couple times...

I meant that I only use these packs when carrying large amounts of water. Otherwise it is something much lighter, and with a much lighter load.

My venttilated packs are used for specific tasks, which is why I have a collection of packs :)

Usually when I do skyline, my base weight is around 4 lbs or less, but a lot of water. By the time I get up that last chute near the tram motor, almost all the water is gone.

To be honest, I think people are too concerned with sweaty backs. I just ignore it. The suggestion that if you are getting warm, you can carry it on one shoulder for a short period of time. It is not a technique that I use much. Most of our packs must weigh a lot less than a loaded computer bag.

I've tried Gregory Z-doesn't fit. Exos is great until I put 20 pounds in it. Deuter is too heavy. So far it's Stratos 36- I like most features, but Atmos back is better (I haven't tried Atmos 35-which is panel loader, no rain cover, and those stupid side mesh pockets with holes in them.

That said, North Face Solaris-looks like a big book bag-with substantial padded hip belt is about perfect as a travel bag-carries weight great for me UNLIKE kELTY 2650-WHICH HURTS LOWER BACK)

BUT-the North Face is hot as hell.

Any thoughts on whether trampoline really helps keep cooler and whether it will last-the trampoline mesh system looks like it will weaken over time and become useless.

Any thoughts and experiences: ie. Old fashioned hot bag that fits, vs hi-tech bag with air flow

Nick Said:>To be honest, I think people are too concerned with sweaty backs. I just ignore it.

Yup. Usually my load is light and stable enough that I just loosen the shoulder straps a bit and let the pack hang off my back a bit. When I'm carrying a lot of food/water, I get a sweaty back and live with it. I love a quick wash at stream crossings.

My son and I had Atmos packs (50L and 65L) and liked the ventilated back, but the mesh/arch area took up too much room in the pack. We both LOVE our Exos 46 packs, perfect amount of ventilation and pack room. Still looking for the "right" frame-less pack to try someday, but for now the Exos is hard to beat.

I had a Venturi 40 and it was very comfortable. Got rid of it, only because it wasn't really the type of pack I needed. It was, however, very sturdy for its weight, and carried moderate loads very well. The only thing to look at with this type of pack is whether or not the curved stays intrude too much into the body of the pack for you. They do make it slightly more difficult to pack, but it's a marginal difference really.

You're going to have some trouble finding a decent panel loader though, they're becoming increasingly rare it seems. I'd be too leery about a zipper failure making the pack useless out on the trail, so I steer clear of zippered packs.

Vaude makes a bunch of ventilated packs and I like their packs in general. They show design features that come from someone who uses backpacks. I like their use of line rather than webbing for compression straps and ice axe loops. I got a Hiker 20 on Steep and Cheap last week that is a nice little bit of pack engineering.

Marmot has made some too. My favorite day pack is a Misty Falls that has a vaulted mesh back.

This kind of goes back to the pros and cons of the late Colin Fletcher's Trailwise external pack frame that had an enormous mesh back band.

Many internal frame packs are touted to have ventilated back panels, but only a few have suspended mesh panels, and of those, the only ones over 2000 c.i. that I could find with the mesh connected along its entire perimeter were the Ospreys.

This is important to me, because I find that it is only when the entire perimeter of the mesh is stretched and connected to the pack that it molds to my back and flexes well as I move. It is also nice to avoid creating an inaccessible dream spot for biting insects to get at your back.

Otherwise, why not just use an inverted U-shaped tubular frame with curved crossbars, stretch a wide mesh band and a waist belt harness horizontally around it, and attach whatever pack you like that fits. And with tough caps over the bottoms of the legs, the pack bottom is protected from a lot of abrasion.

There was a pack of this type made by Alpine Designs that used an ABS hour-glass shaped tubular frame, with the mesh connected all around. This is what I use, with all the fabric but the backband replaced by 4 oz. (total) Spectra gridstop.

It was because this pack was so comfortable to carry doing trail work, with heavy equipment thrown into it and the waist belt removed, that I converted it for regular BP, adding an Osprey moldable hipbelt. The pack is about 3000 c.i. and weighs just over 3 lbs with the fairly heavy older style Osprey belt.

Ray's post suggests that Osprey has reduced the distance between the mesh back and the pack back, but it does not sound like that from Joe Clement's post. Osprey probably uses a lot of tension and distance to avoid complaints about things poking through into customers' backs (there may be no heavy foam or frame sheet). Unfortunately, this not only reduces pack space; but as also noted on this thread, pushes the center of gravity of the load backward, cancelling out a lot of the comfort gained from the suspended mesh back panel.

In remodelling my own, and making another pack with an aluminum tube hour-glass frame and suspended mesh back panel, I learned that the ABS works better for loads under 30 lbs (total) because it is more flexible, and that the dimensions in the design must be extremely precise for the panel to come out stretched tight. Sort of like a geodesic tent design. So I imagine it is a bit of a challenge for the manufacturers to build to this design, but if Alpine Designs could do it, it can be done today.

In the meantime, when my home-made item wears out, I will buy an Osprey, and maybe modify it a little to move the center of gravity forward if they haven't done that already. With this type of design, while I'm sure my back sweats, I have never felt it. It really is a lot more comfortable, and I wouldn't settle for anything less were I to go trekking in the tropics (fat chance).Sam

There are trade-offs for everything. No one makes the perfect pack for all conditions. For me, I am willing to sweat to save 2+ lbs in most situations, especially when another couple lbs will increase my base weight by 30% or even more.

I still have my old Kelty Serac external frame. I think it is the largest bag they ever made, and can carry a ton of weight, and has two mesh panels. But it has been a long time since I used it. It is much cooler than some of large internal frames I have owned/own. Bottom line is that most of the time my base weight is well below 10lbs, and often below 5lbs and that is the most important thing to me.